Correlation of energy loss and crystallographic transformation of ion-irradiated carbon foils

Fast ions in the energy range 100-400 keV traversing carbon foils of typically 5-15 μg/cm2 surface density suffer a specific energy loss of 1-1.7 keV/μgcm-2 per ion. The energy deposited in the foil causes a continuous crystallographic transformation (graphitization) leading to an increase of the mass density and also of the energy loss per ion (at constant surface density). The rate of the energy loss variation is investigated as a function of the atomic number of the projectile, the current density, and the projectile energy. It is shown that the increase of energy loss is a consequence of the crystallographic transformation and may be interpreted in terms of the Lindhard-Scharff theory. (orig.)